Mark Houlahan
Tech Editor, Mustang Monthly
August 3, 2004

Measuring the amount of incoming air to your engine is the job of themass air meter. Even more critical is for the mass air meter to relaythis airflow information back to your Mustang's Electronic EngineControl so that the proper engine-management outputs are kept in check.For instance, without this information, the EEC wouldn't know how muchfuel to add to the engine. While the stock mass air meter is calibratedto the stock injector size, if you increase injector sizes or exceed theairflow capabilities of the meter (commonly called "pegging" the meter),you'll run into an electronic "wall," thus the need for a larger andmore accurately calibrated mass air meter.

J.R. Granatelli's Granatelli Motor Sports has inked a deal with HitachiAutomotive Products to bring high-quality mass air meters to theperformance-minded public. GMS calibrates the meters in-house for anyone of dozens of applications, meaning the meters can be recalibrated asyou change injector size or inlet configurations (such as cold-air kitsand so on).

For this Tech Inspection we used the Big Mouth mass air meter, whichretails for approximately $399 for the 19-lb/hr calibrated base meter(cold-air tuning and other injector sizing cost a bit more). The newHitachi-based meters with the '86-'93 inlet pipe are available inseveral colors and feature the '94-and-later four-bolt flangearrangement so they can be used in any year Mustang or Ford product.They come with the proper mounting option for the year ordered.

The meters also sport the newer six-wire sensor connector, which can beused in earlier applications with the GMS sensor adapter harness(included when required).

1. Since the new GMS mass air meter includes a high-flow filterand inlet tube, you'll need to ditch your stock airbox and inlet hose.Begin by removing the two retaining nuts for the airbox assembly to theinner fender structure.
2. Once the airbox is loose, work your way up the inlet tract andremove the two mass air meter retaining bracket bolts. Then loosen thehose clamp at the throttle body. Pop the inlet hose off the throttlebody and disconnect the mass air meter's electrical connection. Lift theinlet duct, the mass air meter, and the airbox out of the enginecompartment as an assembly.
3. If your throttle body requires the included silicone hosesleeve adapter, slide it onto the throttle body first.
4. Position the aluminum cast inlet tube into place, ensuring itclears the strut tower. Secure the hose clamp at the throttle body.Position the meter for adequate clearance, and secure the remainingclamps along the inlet tract to secure the meter.
Here's the meter installed, which took all of 10 minutes to achieve. We chose the yellow mass air meter to add a bit of flair under the hood and to match the Chrome Yellow paint on this notch. Unfortunately, the adapter harness was on backorder at our deadline, so we didn't get to test the meter. But GMS should have plenty in stock by the time you read this.